Method and device for hot air leak detection in aircraft installation by wire diagnosis

In most aircrafts, hot air leak detection loops are formed by thermo-sensitive cables having temperature dependent characteristics. These wires are installed along air ducts in order to be able to react to temperature changes induced by leaks. Hence, an alert is sent to the cockpit. However, with old configurations, this alert does not include the leak localization information. Classic methods based on load measurement allowing defect localization are not accurate enough as they do not take into account the cable aging and junction degradation. This may cause false alerts. The proposed method uses multi-carrier reflectometry: MCTDR (Multi-Carrier Time Domain reflectometry). Advantageously, the MCTDR measures allow our device to be superimposed on the already installed systems without interfering with current signals. Moreover, we can detect and locate precisely any abnormality or change on cable. The reflectometer measures received signal and compares it to a given reference in terms of peaks magnitudes. A hot point is detected when the peak magnitudes of a given number of successive reflectograms are increasingly smaller than reference. This is being caused by a decrease in local value of impedance. The device allows the detection and localization of defects with a good accuracy. Moreover, we deduce the value of the temperature at the hot area by computing its impedance. This tool can be used in maintenance mode or embedded mode allowing preventive maintenance and avoiding aircraft on ground (AOG) situation.